U.S. Pat. No. 4,302,330, dated Nov. 24, 1981, describes a typical filtration apparatus of the kind to which this invention relates. The apparatus provides for the intermittent rotation of a cylindrical filter element about its axis in order to effect “spin-cleaning.” Solid matter filtered out of the fluid is thrown off the filter element by inertia. Similar filters are known, in which the filter element is rotated continuously as filtration takes place, in order to avoid accumulation of solid matter on the filter element.
When a filter element, made from ceramic, diatomaceous earth, stainless steel, or any of various polymeric materials, is rotated during filtration, it can be used for extended periods of time, and becomes effectively non-disposable. Non-disposability is a significant advantage because of the high cost of these advanced filtration materials.
Sometimes, however, difficult situations are encountered, in which even a rotating filter element will become fouled, and require removal for cleaning, or replacement. In such a situation, either the process must be shut down temporarily, or an auxiliary filter must be provided in order for the process to continue.